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Message: <blockquote data-quote="Woodcutter" data-source="post: 2524228" data-attributes="member: 10230"><p>When I am really serious about accuracy and consistency, in my opinion there is only one chronograph to use.  This the brand that the ammunition companies and the writers of the reloading manuals use.  I am talking about the Oehler model 35P proof channel chronograph.  With all others, I am just guessing.  The 35P actually takes two velocity measurements and compares the two.  It lets you know if you can trust the figure or if something happened to cause an erroneous reading.  For those of you who own two or more chronographs, or if you own one and know someone else who owns one, could you please try this and report back the results?  Place the two chronographs in line, front to back so that you can get a reading from both of them for the same shot.  If you get the same reading from both of them on every shot, then you can trust every shot.  But what if one of them reads 973 FPS and the other reads 861 FPS for the same shot?  That has happened to me with two Chrony brand chronographs. With just a single reading for each shot, you do not know if it is accurate or if it was reading a pressure wave or the actual bullet on both screens, for example.  In developing accurate long range rifle loads, the standard deviation (SD) is just as important, if not more important, than the average velocity.  I have seen the SD vary between two chronographs by as much as a factor of three, measuring the same shot string using the back to back method.  That is why you need the proof channel.  With it you know if a velocity reading is in error, and you can remove it from the SD calculation.  You get a much more accurate measure of the consistency of your load and rifle that way.  Before I discovered this, I wasted hundreds of dollars in reloading components, not to mention many hours of my time, chasing that elusive accurate, consistent long range load.  I could have used this wasted money to buy several Oehler Chronographs.</p></blockquote><p></p>

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